1. Field of the Invention
The present invention is related to a crimp terminal including a conductor crimping portion having a U-shaped cross section and including a pair of conductor caulking pieces, and a crimping structure with respect to an electrical wire of the crimp terminal.
2. Description of the Related Art
Conventionally, a crimp terminal is known which is crimped to an electrical wire when a pair of conductor caulking pieces caulks a conductor of the electrical wire by being bent inward so as to wrap the conductor (for example, refer to Japanese Patent Application Laid-open No. 2009-135022). In a crimping structure with respect to an electrical wire of a crimp terminal disclosed in Japanese Patent Application Laid-open No. 2009-135022, a pair of conductor caulking pieces caulks a conductor by being bent so that one conductor caulking piece overlaps on an upper side of the other conductor caulking piece. Specifically, both the conductor caulking pieces are bent so as to overlap each other.
FIGS. 7 and 8 illustrate an example of such a conventional crimping structure with respect to an electrical wire of a crimp terminal.
FIG. 7 is a perspective view illustrating an appearance of a crimping structure in which a conventional crimp terminal is crimped to an electrical wire.
FIG. 8 is a view illustrating a crimping process in the crimping structure illustrated in FIG. 7.
In each figure, a reference sign 100 denotes a crimp terminal, a reference sign 150 denotes an electrical wire, and reference signs 141 and 143 denote a lower die (anvil) and an upper die (crimper) of a crimp tool.
As illustrated in FIG. 7, the crimp terminal 100 includes an electrical connection portion 110, a conductor crimping portion 120, and a coating caulking portion 130. The electrical connection portion 110 is connected to such as a mating terminal on one end side (front side) in a longitudinal direction thereof (hereinafter the direction is described as “a front and back direction”, and a direction orthogonal to the front and back direction is described as “a right and left direction”). The conductor crimping portion 120 is caulked, on the other end side (back side), to an exposed conductor 151a arranged on a tip of an electrical wire 150. The coating caulking portion 130 is caulked to an insulating coating 153 of the electrical wire 150.
In the above configuration, the exposed conductor 151a is a portion exposed from the insulating coating 153 at the tip of the electrical wire 150 including a conductor 151 and the insulating coating 153. The conductor 151 includes multiple bundles of strands in the form of such as a twisted wire. The insulating coating 153 is formed so as to coat a periphery of the conductor 151.
The electrical connection portion 110, the conductor crimping portion 120, and the coating caulking portion 130 include a common bottom plate 105.
As illustrated in FIG. 8(a), the conductor crimping portion 120 is a portion in which a pair of conductor caulking pieces 121a and 121b are erected on both end sides in the right and left direction of the bottom plate 105 extending continuously from the electrical connection portion 110. The conductor crimping portion 120 is formed so as to have a U-shaped cross section before caulking.
When the conductor crimping portion 120 of the crimp terminal 100 is crimped to the exposed conductor 151a, as illustrated in FIG. 8(a), first the crimp terminal 100 is mounted on a lower die 141, and the exposed conductor 151a is inserted between the conductor caulking pieces 121a and 121b and mounted on the bottom plate 105. As illustrated in FIGS. 8(b) to 8(e), by gradually descending an upper die 143, a tip side of the conductor caulking pieces 121a and 121b on an inner surface of the upper die 143 is gradually tilted inward, and finally the conductor caulking pieces 121a and 121b are bent so as to wrap the exposed conductor 151a. Thereby, as illustrated in FIG. 8(f), the exposed conductor 151a of the electrical wire 150 is caulked by the conductor crimping portion 120 and closely contacted to an upper surface of the bottom plate 105 and the conductor caulking pieces 121a and 121b. At this time, as illustrated in FIG. 8(f), a pair of the conductor caulking pieces 121a and 121b caulks the exposed conductor 151a by being bent so that the one conductor caulking piece 121a overlaps on an upper side of the other conductor caulking piece 121b. In the coating caulking portion 130 is caulked to the insulating coating 153 of the electrical wire 150 in advance as with the above description before caulking of the conductor crimping portion 120.
In the case where the conductor crimping portion 120 is crimped to the exposed conductor 151a of the electrical wire 150 by caulking the conductor caulking pieces 121a and 121b, it is expected that a conductive metal included in the crimp terminal 100 and the exposed conductor 151a are stuck, and the crimp terminal 100 and the electrical wire 150 are electrically, mechanically, and strongly bonded.
However, in a conventional crimp terminal and crimping method, the conductor caulking pieces 121a and 121b might be opened because a force (restoring force) in the direction in which the conductor caulking pieces 121a and 121b return to an original shape acts such as by spring back thereof after being caulked. As a result, a contact pressure with respect to the conductor 151 might become weak.
In the case where a contact pressure with respect to the exposed conductor 151a of the conductor caulking pieces 121a and 121b is not secured, a clamping force becomes weak, and therefore mechanical strength of a crimping portion might not be secured. Further, a proper resistance of the crimping portion cannot be secured. Specifically, electrical connection performance might be reduced since a contact resistance is increased.
Furthermore, in consideration of easiness in downsizing and recycling a vehicle, recently an aluminum electrical wire including aluminum as a conductor of an electrical wire can be used. Aluminum is less strong and ductile than copper and is easy to cause stress relaxation. Therefore, in the case of using an aluminum electrical wire, a contact pressure is especially likely to decrease.